Early onset diabetes mellitus, or Type I diabetes, is a severe, childhood, autoimmune disease, characterized by insulin deficiency that prevents normal regulation of blood glucose levels. Insulin is a peptide hormone produced by the xcex2 cells within the islets of Langerhans of the pancreas. Insulin promotes glucose utilization, which is important for protein synthesis as well as for the formation and storage of neutral lipids. Glucose is also the primary source of energy for brain and muscle tissue. Type I diabetes is caused by an autoimmune reaction that results in complete destruction of the xcex2 cells of the pancreas, which eliminates insulin production and eventually results in hyperglycemia and ketoacidosis.
Insulin injection therapy has been useful in preventing severe hyperglycemia and ketoacidosis, but fails to completely normalize blood glucose levels. Although insulin injection therapy has been quite successful, it does not prevent the premature vascular deterioration that is the leading cause of morbidity among diabetics today. Diabetes-related vascular deterioration, which includes both microvascular deterioration and acceleration of atherosclerosis, can eventually cause renal failure, retinal deterioration, angina pectoris, myocardial infarction, peripheral neuropathy, and atherosclerosis.
A promising treatment for diabetes, islet transplantation, has been in human clinical trials for over ten years. Unfortunately, the results where Type I diabetes is the underlying etiology are poor. There have been many successes with islet transplantation in animals, but only where the animals are diabetic due to chemical treatment, rather than natural disease. The only substantiated peer reviewed studies using non-barrier and non-toxic methods and showing success with islet transplants in naturally diabetic mice use isogeneic (self) islets. The isogenic islets were transplanted into already diabetic NOD mice pre-treated with TNF-alpha (tumor necrosis factor-alpha); BCG (bacillus Calmette-Guerin, an attenuated strain of mycobacterium bovis); and CFA (complete Freund""s adjuvant), which is an inducer of TNF-alpha (Rabinovitch et al., J. Immunol. (1997)159(12):6298-303). This approach is not clinically applicable primarily because syngeneic islets are not available. In the allograft setting of islet transplantation, the grafts are rejected presumably due to autoimmunity. Furthermore, diabetic host treatments such as body irradiation and bone marrow transplantation are too toxic in Type I diabetes patients, rendering the short-term alternative of insulin therapy more attractive.
I previously developed a transplant method to introduce allogeneic and xenogeneic tissues into non-immunosuppressed hosts, in which the cells are modified such that the donor antigens are disguised from the host""s immune system (Faustman U.S. Pat. No. 5,283,058, hereby incorporated by reference). Generally, masked islets or transgenic islets with ablated class I are only partially protected from recurrent autoimmunity in spontaneous non-obese diabetic (NOD) mice (Markmann et al., Transplantation (1992) 54(6):1085-9). There exists the need for a treatment for diabetes and other autoimmune diseases that halts the autoimmune process.
The present invention provides a novel method for reversing existing autoimmunity.
Accordingly, the invention provides a method for increasing or maintaining the number of functional cells of a predetermined type (e.g., islet cells) in a mammal, involving the steps of: (a) providing a sample of cells of the predetermined type, (b) treating the cells to modify the presentation of an antigen of the cells that is capable of causing an in vivo autoimmune cell-mediated rejection response, (c) introducing the treated cells into the mammal, and (d) prior to, after, or concurrently with step (c) treating the mammal to kill or inactivate autoimmune cells of the mammal.
In preferred embodiments, step (b) involves eliminating, reducing, or masking the antigen, which is preferably is MHC class I. Such methods are known, and are described, e.g., in Faustman, U.S. Pat. No. 5,283,058.
Preferably, step (d) involves administering to the mammal tumor necrosis factor-alpha (xe2x80x9cTNF-alphaxe2x80x9d), or a TNF-alpha inducing substance, (i.e., an agonist). As will be explained in more detail below, the TNF-alpha signaling pathway is an inflammatory pathway that effectively brings about killing of the autoimmune cells that attack the desired cells. There are many methods for stimulating TNF-alpha production, including the following: vaccination with killed bacteria or toxoids, e.g., BCG, cholera toxoid, or diphtheria toxoid; induction of limited viral infections; administration of LPS, interleukin-1, or UV light; activation of TNF-alpha producing cells such as macrophages, B-lymphocytes and some subsets of T-lymphocytes; or administration of the chemotatic peptide fMET-Leu-Phe; CFA-pacellus toxoid, Mycobaterium bovis bacillus, TACE (a metalloproteinase that mediates cellular TNF-alpha release), hydrozamates, p38 mitogen activated protein (xe2x80x9cMAPxe2x80x9d) kinase, and viral antigens that activate NFxcexaB transcription factors that normally protect the cells from apoptosis (i.e., cell death).
Killing of undesired autoimmune cells can also be accomplished by administering agents that act as agonists for the enzyme, TNF-alpha converting enzyme, that cleaves the TNF-alpha precursor to produce biologically active TNF-alpha.
Autoimmune cells can also be killed by administering agents that disrupt the pathways that normally protect autoimmune cells from cell death, including soluble forms of antigen receptors such as CD28 on autoreactive T cells, CD40 on B cells that are involved in protection of autoimmune cells, and CD95 (i.e., Fas) on T-lymphocytes. Other such agents include p75NTF and lymphotoxin Beta receptor (LtbetaR).
The methods of the invention in some respects run counter to current treatment regimens for autoimmune diseases. Many of the major approved therapies for such diseases involve the administration of anti-inflammatory drugs that inhibit the production of TNF-alpha, including COX-2 inhibitors, and TNF antagonists. My studies indicate that these conventional therapies are actually deleterious, in that they bring about expansion of the population of harmful autoimmune cells in the patient, increasing the number and severity of lesions and autoreactive infiltrates. In addition, many of these anti-autoimmune inflammatory drug therapies cause severe re-bound disease after discontinuation. For example, treatment with anti-inflammatory agents actually increases the number of lymphocyte infiltrates in the pancreas of a diabetic. Once treatment is discontinued, these lymphocytes regain their normal function, resulting in a heightened autoimmune response.
The methods of the invention can be used to treat any of the major HLA class II-linked autoimmune diseases characterized by disruption in MHC class I peptide presentation and TNF-alpha sensitivity. These diseases include, for example, type I diabetes, rheumatoid arthritis, SLE, and multiple scelorosis. The method can be used in any mammal, e.g., human patients, who have early pre-symptomatic signs of disease, or who have established autoimmunity.
The invention also provides a method for increasing or maintaining the number of a predetermined type e.g., islet cells, in a mammal by the steps of (a) treating the mammal with an agent that kills or inactivates autoimmune cells of the mammal; (b) periodically monitoring the cell death rate of the autoimmune cells; and (c) periodically adjusting the dosage of the agent based on the information obtained in monitoring step (b).
In any of the methods of the invention in which TNF-alpha is administered or stimulated, two agents can be used together for that purpose, e.g., TNF-alpha and IL-1 can be used in combination therapy, as can any other combinations of agents.
In addition, the invention provides a method for diagnosing an autoimmune disease or predisposition to such a disease in a mammal (e.g., a human patient). The method includes the steps of (a) providing peripheral cells from a mammal; (b) treating these cells with a TNF-alpha treatment regimen and; (c) detecting cell death in the peripheral cells, where an increase in cell death, when compared with control cells, is taken as an indication that the mammal has an autoimmune disease or predisposition to such disease. This diagnostic method can be used for any mammal, however, the preferred mammal is a human patient. Peripheral cells that can be used in this method are, for example, splenocytes, T lymphocytes, B lymphocytes, or cells of bone marrow origin and in step (b) of the method, these cells are preferably treated with TNF-alpha.
By xe2x80x9cfunctional cell,xe2x80x9d is meant cells that carry out their normal in vivo activity. In certain preferred embodiments of the invention, it is preferred that the cells are capable of expressing endogenous self peptide in the context of MHC class I.
By xe2x80x9cpredetermined type,xe2x80x9d when used in reference to functional cells, is meant that one may select a specific cell type. For example, one skilled in the art may decide to carry out the method of the present invention in order to increase or maintain the number of functional islet cells in the pancreas. In this example, the predetermined cell type is islet cells.
By xe2x80x9cclass I and peptidexe2x80x9d is meant MHC class I presentation of peptide (i.e., self peptide) on the cell surface. Cytoplasmic antigens are believed to be processed into peptides by cytoplasmic proteases and at least in part by the proteasome, a multicatalytic proteinase complex of which the Lmp2 protein, discussed herein, is associated. The process of MHC class I presentation is thought to include formation of a complex between the newly synthesized MHC class I molecule, including a glycosylated heavy chain non-covalently associated with xcex22-microglobulin, and peptide within the rough endoplasmic reticulum of the cell. Thus, xe2x80x9cclass I and peptidexe2x80x9d refers to the MHC class I/peptide complex as it is presented on the cell surface for education of the immune system.
By xe2x80x9ckillingxe2x80x9d or xe2x80x9ckillsxe2x80x9d is meant to cause cell death by apoptosis. Apoptosis can be mediated by any cell death pathway. According to the present invention, cells that are susceptible to killing are defective in protection from apoptosis due to a defect in a cell death pathway.
xe2x80x9cAutoimmune cells,xe2x80x9d as used herein, includes cells that are defective in protection from apoptosis. This defect in protection from apoptosis can be in the pathway linked to TNF-induced apoptosis, or an apoptotic pathway unrelated to TNF. Autoimmune cells of the present invention include, for example, adult splenocytes, T lymphocytes, B lymphocytes, and cells of bone marrow origin, such as defective antigen presenting cells of a mammal.
By xe2x80x9cdefectivexe2x80x9d or xe2x80x9cdefectxe2x80x9d is meant a defect in protection from apoptosis.
By xe2x80x9cexposurexe2x80x9d is meant exposure of a mammal to MHC class I and peptide (i.e., self peptide or endogenous peptide) by any means known in the art. In one preferred embodiment, exposure to MHC class I and peptide is carried out by administering to the mammal an MHC class I/peptide complex. In other preferred embodiments, exposure to MHC class I and peptide occurs by exposing the mammal to cells that express MHC class I and peptide.
By xe2x80x9ccells capable of expressing MHC class I and peptidexe2x80x9d is meant, for example, cells that are class I+ or cells that are class Ixe2x88x92/xe2x88x92 (e.g., cells having a mutation in the xcex22M gene) but that are reconstituted in vivo by a compensatory component (e.g., serum xcex22M).
By xe2x80x9cmaintenance of normal blood glucose levelsxe2x80x9d is meant that a mammal is treated, for example, by insulin injection or by implantation of a euglycemic clamp in vivo, depending on the host being treated.
By xe2x80x9clmp2 gene or an equivalent thereof,xe2x80x9d is meant a cell that has a defect in prevention of apoptotic cell death, for example, a cell that has an ablation at a critical point in an apoptotic cell death pathway. In another aspect, xe2x80x9clmp2 gene or an equivalent thereofxe2x80x9d means that a cell has a mutation in the lmp2 gene or a gene that carries out a function the same as or similar to the lmp2 gene (i.e., a gene encoding a proteasome subunit). Alternatively, the phrase xe2x80x9clmp2 gene or an equivalent thereofxe2x80x9d can be used to refer to a cell that has a mutation in a gene that encodes a regulator of the lmp2 gene or another component of the proteasome complex. For example, a human homolog of the murine lmp2 gene is an equivalent of the lmp2 gene according to the present invention. As but another example, a gene that carries out the same or similar function as the lmp2 gene, but that has a low amino acid sequence similarity, would also be considered as an equivalent of the lmp2 gene according to the present invention.
xe2x80x9cCombination therapy,xe2x80x9d or xe2x80x9ccombined therapy,xe2x80x9d as used herein, refers to the two-part treatment for increasing the number of functional cells of a predetermined type that includes both (1) ablation of autoimmune cells, and (2) re-education of the host immune system.
By xe2x80x9cTNF-alpha induction,xe2x80x9d xe2x80x9cTNF-alpha treatment regimen,xe2x80x9d or xe2x80x9cTNF-alphaxe2x80x9d includes the administration of TNF-alpha, agents that induce TNF-alpha expression or activity, TNF-alpha agonists, agents that stimulate TNF-alpha signaling, or agents that act on pathways that cause accelerated cell death of autoimmune cells, according to the invention. Stimulation of TNF-alpha induction (e.g., by administration of CFA) is preferably carried out prior to, after, or during administration (via implantation or injection) of cells in vivo.
By xe2x80x9ceffective,xe2x80x9d is meant that the dose of TNF-alpha, or TNF-alpha inducing agent, administered, increases or maintains the number of functional cells of a predetermined type in an autoimmune individual, while minimizing the toxic effects of TNF-alpha administration. Typically, an effective dose is a reduced dose, compared to doses previously shown to be ineffective at treating autoimmune disease, particularly established autoimmune disease.
The methods of the invention provide, for the first time, effective reversal of naturally-occurring (as opposed to chemically induced) mediated diseases such as type I diabetes.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiment thereof, and from the claims.